$ perl -w -E '@values = split ",", "1,2,3,4", -1; say join ",", @values'
1,2,3,4
$ perl -w -E '@values = split ",", ",,3,", -1; say join ",", @values'
,,3,
$ perl -w -E '@values = split ",", ",,,", -1; say join ",", @values'
,,,